I've had the same gri gri I bought not long after they came out, and use it all the time. Never had any issues with it; still works as good as it did when new.
The new one is supposed to be better with skinny ropes. Since I don't use a skinny rope, if I ever lose mine I will be looking for a replacement instead of buying a new one.
You don't seem to be a skinny rope guy.... that said, the 10 and probably the 10.5 mm would be fine.